1. Field of the Invention
The present invention relates to a drive recorder that records driving condition data (including image data and traveling data) of a vehicle on the occasion of a traffic accident or dangerous driving, etc.
2. Description of Related Art
In recent years, as means that contributes to reduction of traffic accidents and to analysis of a traffic accident after the occurrence of the traffic accident, a drive recorder is mounted in more and more vehicles. As an example of a conventional technology related to the drive recorder, JP-A-2008-52230 (hereinafter, referred to as Patent Document 1) can be cited.
Various manufacturers have made efforts to develop various technologies related to trigger judgment by the drive recorder (judgment on occurrence of a particular driving behavior in response to which an operation should be performed, for example, to store driving condition data in a nonvolatile manner or to alert a driver). As an example of a conventional technology related to the trigger judgment by the drive recorder, WO 07/058,357 pamphlet (hereinafter, referred to as Patent Document 2) can be cited.
Certainly, the provision of the above-described conventional drive recorder in a vehicle contributes to the reduction of traffic accidents, because a driver, being unwilling to have a traffic accident caused by his or her negligence or his or her dangerous driving recorded in the drive recorder, sticks to safe driving if the conventional drive recorder mentioned above is mounted in the vehicle that he or she drives. Furthermore, if a driver should be involved in a traffic accident despite the fact that he or she deserves no blame for the traffic accident, the driver's innocence can be proved by analyzing, after the occurrence of the traffic accident, the driving condition data recorded in the drive recorder mounted on the vehicle.
In the above-described conventional drive recorder, the trigger judgment is typically performed by sequentially calculating a differential value X(t) (=Gmax(t)−Gmin(t)) by subtracting the minimum value Gmin(t) from the maximum value Gmax(t) of ceaselessly changing vehicle acceleration data G(t) in a unit time (from time (t−α) to time t) or its absolute value |X(t)| and comparing the acquired value with a predetermined threshold value Xth (see FIGS. 11A and 11B).
However, such a trigger judgment algorithm is so sensitive that it responds to an acceleration shift attributable to a road surface condition (e.g. an uneven road surface), and thus a trigger is activated even in driving over a railroad crossing to unnecessarily activate a nonvolatile storage operation of recording the driving condition data or an unnecessary operation of warning the driver. If such erroneous trigger judgment is repeatedly made, leaving the driver uninformed of whether a warning is due to his or her own dangerous driving behavior (e.g. sudden acceleration, sudden steering, sudden breaking) or due to erroneous trigger judgment, the driver eventually becomes accustomed and insensitive to the warnings that are given so often while he or she is driving, and this disadvantageously damages the safe-driving promoting effect that is originally expected from the drive recorder.
Patent Document 2 discloses a driving behavior recording device that includes an erroneous detection reduction processing unit that judges, based on a combination of a wave height and a pulse width of a pulse waveform in data (including acceleration data) of a detected driving behavior, whether the data is particular behavior data or pseudo-behavior data which is erroneously detected as the particular behavior data, and stores the data in a storage medium only when it is judged to be the particular behavior data.
However, with the conventional technology, it is necessary to compare at least one (preferably, more than one) of each of the two parameters of the wave height and the pulse width needs to be compared with a threshold value, and this makes the trigger judgment processing complex, and furthermore, in a case, for example, where a vehicle runs on an uneven road surface to receive vibration while it is being accelerated, the pulse height and the pulse width of the pulse waveform each exceed a predetermined threshold value, which disadvantageously leads to erroneous trigger judgment.